Background

Chirped gratings with variable period, or spatial frequency, are well known in optical science and are widely used for spectral filtering and analysis. However, the main part of the chirped gratings is made in fiber geometry. The use of volume chirped gratings is restricted by the lack of available photosensitive materials which provide high sensitivity, low losses, and stability of volume in the processes of exposure and development. The last feature is extremely important for chirped gratings because of necessity for precise control of spatial distribution of grating period.

Technology

Researchers at the University of Michigan have fabricated stretchers and compressors for ultrashort laser pulses with high efficiency, high laser-induced damage threshold, and protected from misalignment by means of recording of high efficiency volume gratings with variable period (chirped) in PTR glass. The main approach of the present invention is a combination of properties of high efficiency volume Bragg gratings in PTR glass which allow achieving very large sizes (tens of millimeters) of both transverse apertures and in-depth direction with highly homogeneous spatial grating profile, and ideology of stretching and compression of short pulses for power amplification by chirped fiber gratings. This invention is a continuation in part of previous inventions which describe a method of fabrication of high efficiency volume diffractive gratings in PTR glass. The present invention also enables creation of a new generation of high power femtosecond laser systems.